In order to examine the presence of abnormalities in blood-clotting factors, a blood clotting test is performed as a clinical test. In the blood clotting test, for example, prolongation of activated partial thromboplastin time is used as an indicator of abnormalities in blood-clotting factors. The prolongation of activated partial thromboplastin time is assumed to be due to lupus anticoagulant or the like.
In the lupus anticoagulant screening test, a method of using a reagent containing a low level of phospholipids is performed. The use of the reagent containing a low level of phospholipids easily causes an inhibitory reaction on the phospholipids due to lupus anticoagulant. Therefore, this method allows the prolongation of clotting time caused by lupus anticoagulant to be easily detected. There is a reagent for detecting lupus anticoagulant such as an activated partial thromboplastin time kit PTT LA reagent “RD” Package Insert, Revised December, 2012 (third edition), [online], [searched on Jul. 28, 2015], Internet <URL:http://www.info.pmda.go.jp/downfiles/ivd/PDF/700025_21700AMY00198000_A_01_02. pdf> (Non-Patent Literature 1).
The clotting time in the case of measurement of normal plasma as a specimen using the reagent described in Non Patent Literature 1 is in the range of 29 to 43 seconds. This clotting time is longer than the clotting time in the case of measurement using a usual reagent for measuring activated partial thromboplastin time which is not a reagent for detecting lupus anticoagulant. Accordingly, it is desirable to prevent the clotting time from becoming too long.